In a mounting process of electronic parts, an assembly line has been composed by utilizing individual feature of each mounting machine, and thereby manufacturing a PCB. For example, in a mounting process of micro-chip parts, a high-speed surface mounting machine mounts the parts, and when mounting QFP (quad flat package) and others having so narrow spacing between pathways of leads or pins that a precise mounting is required a robot type machine featuring precise mounting is employed after the process using the high-speed machine. Such an operation of combining different types of machines improves a quality of an efficiency of the entire assembly line. It is also a well-known operation method that a plurality of the same machines is placed in one assembly line in order to shorten a tact time of the assembly line. When determining compositions of these conventional assembly lines, a line manager has to do the following jobs manually.
1. Collect such data from the parts list for the specific PCB as numbers of parts, available machines for mounting the parts, individual tact time for mounting each part of each machine, maximum loadable numbers of parts into each machine.
2. Determine whether plural assembly lines are necessary for manufacturing this type of PCB, e.g. determine whether independent lines are necessary for insertion process, surface mounting process, and semiconductor mounting process. Then, assign each part to a line, and the following policy must be considered when a line composition is determined.
2-1. In general, assign a maximum loadable parts into a machine of the highest mounting speed among the group of machines. Surplus parts from the machine, or non-loadable parts into the machine are assigned to another machine of next higher mounting speed. The same procedure follows until all parts are assigned.
2-2. Reassign the parts within each line in order to smooth out the load to each machine so that a specific machine may not take an exceptionally longer tact time. For this purpose, an optimizing simulation using a computer are already available as a prior art.
2-3. After smoothing out, if the tact time of each line satisfies the desirable level, this line composition is finalized as an actual mounting line. If the tact time of each line could not satisfy the desirable level, a next possible machine is supplemented to the line composition so that the total tact time of the line may satisfy the desirable level. This procedure follows until the total tact time of the lines satisfies the desirable level.
The above procedure, however, leaves several problems to factory staff;
(1) This kind of manual procedure requires a great deal of time and labor for finalizing a desirable line composition, in particular, when planning an annual business plan, a common line composition must be finalized for plural types of PCBs. In this case, try & error calculations are repeated until every tact time of lines for each type of PCBs becomes not more than a desirable time. When any PCBs encounter some changes in a trial production, or due to specific changes, the same kind of calculation must be repeated.
(2) When a factory is equipped with sizable equipment, it is not an optimal operation for the entire factory if there is dispersion between each tact time of lines after finalizing the line compositions for plural types of PCBs. In this case, a line composition of each type of PCBs could not be finalized manually because calculations should be in too many numbers of combinations between sizable equipment and plural types of PCBs.
(3) Only specific line managers who know in detail about mounting conditions of equipment, e.g. each tact time of all equipment, can manage the above procedures and calculations, and ordinary workers cannot follow the procedure nor manage the calculations.